Apple is helping police in China investigate an accident in which a woman was killed by an electric shock when answering a call on her iPhone 5 while it was charging, just after she got out of the bath.

Ma Ailun, a 23-year-old living in China's north-western Xinjiang region and a former flight attendant with China Southern Airlines, was electrocuted last Thursday when she took a call on the charging mobile telephone, the official Xinhua news agency quoted police as saying on Sunday.

If the details of the fatality are correct, it may point to a flaw with the charger or its connecting wires. The Sina English site quoted the family saying the phone had been bought last December from an Apple store, and was using the original charger. The phone and charger are reported to now be in the hands of police.

"We are deeply saddened to learn of this tragic incident and offer our condolences to the Ma family. We will fully investigate and co-operate with authorities in this matter," Apple said in a statement.

Apple declined to comment on details, such as whether this was an isolated case – though there are vanishingly few documented cases of electrocutions while answering a mobile phone when it is charging. A 2011 report in India suggested that the death by electrocution of a man who answered his phone while it was charging could have been caused by a cheap charger he was using.

The climate in Xingiang can become extremely hot during summer, which could contribute to overloads and failures of electrical insulation and equipment. The leads from a phone charger to the phone itself typically carry 5V and around 1A. However, a current of more than 200mA (0.2A) can be lethal if it passes through the heart. If the charger is not earthed, or if the person taking the call provides a better path for current – say from a damaged wire – then the effect could be lethal.

Someone who was wet after a bath might provide just such a pathway for a lethal current.

However, the snopes.com site, dedicated to debunking urban myths, says it is false to suggest that using a mobile phone while it is charging poses a "general and serious" danger of electrocution, despite stories that have circulated online since at least 2004.

Ma's sister tweeted on Sina's microblog, saying Ma collapsed and died after using her charging iPhone 5 and urged users to be careful, a message that went viral on the site.

In April, Apple apologised to Chinese consumers and altered iPhone warranty policies in its second-biggest market after its after-sales service suffered more than two weeks of condemnation by the state-run media.